Pagoda SL Group
W113 Pagoda SL Group => Drive train, fuel, suspension, steering & brakes => Topic started by: gnj588d on March 21, 2010, 22:33:32
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Just decided to change plugs and points ready for summer. done a search for plug gaps but do not seem to get a constant answer the plugs are NGK BP5ES. the points are set at 40 degrees dwell .My car is a 1966 230. while doing the search I noticed the coil colour is an issue mine is red is this correct. Many thanks Mike.
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There were two coils. The "red" coil is more powerful and is an upgrade. It requires the balast resistor to be matched to it. If you aren't having problems, then you probably have the right resistor.
The Bosch number is a W7DC with W8DC and W9DC being progressively hotter. NGK plug numbers run opposite. The BP7ES is equivalent to the Bosch 7 but the BP6 or 5 will be progresivley hotter. The important thing is that the plugs NOT be resistor plugs (WR7DC). If the old plugs are a nice shade of tan/gray, you are running the best plugs for your tuning. I use a gap of .035 in. or .9mm.
The reason you get slight inconsistencies in the printed specs is because there may be some variation of plug and gap that works best in your car that is not the best for another. It depends on the fuel/air mixture, compression, timing, and what kind of chicken you sacrifice while doing the tune up ritual. The balancing act is the fun of tuning. When you get it right, it's so rewarding.
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...and this also segues into the issue of electronic ignition.
One of the benefits of electronic ignition, be it Pertronix or Crane or whatever, is that because you are removing the switching from the points and moving it to an electronic device, you can have a hotter, or much hotter (higher voltage) coil. The higher voltage coil allows you to have a wider point gap with a larger spark. I had a Crane with stock coil; then went to Pertronix with stock coil, then to the Pertronix Fl;amethrower II coil per their recommendation; they claim 40,000 volts. I opened the plug gap a bit and my runnability (ignition wise) is great. Very clean plugs. I run NGK BP6ES. My restorer never liked Bosch plugs.
This is all part of the fun tuning that Raymond talks about.
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W9DC are no longer available. For a while I was using W9DCo but they're not available either. WR8DC are available but they're resistor type so it looks like I'll be using something else.
One plug I won't use is AC or Champion. They can seize in the head if they're installed for a few years. I find that Bosch plugs are the best for aluminium heads because they use nickle plating on the metal shell of the plug. Nickle is a natural anti seize agent and is used in anti seize paste. NGK appear to be yellow Cad plated which might be as good, but I would still use some anti seize on the threads before installation. I suppose any plug that is installed with anti seize would be OK asc long as it's not resistor type.
One way around this would be to remove the resistors on the spark plug wires but I wouldn't recomend doing that.
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Thanks everyone all done and running like god intended.I wish I lived somewhere near the SL Barn. Thanks again everyone I will raise a glass to you tonight ;D